Conventionally, various operation detecting sensors which detect an operator's operation on an operation surface have been devised. The operation detecting sensors include a capacitance type, a thermal resistance type, a piezoelectric acoustic type and an infrared sensor type. To detect a pressing force on an operation surface, it is necessary to install another press detecting sensor different from these operation detecting sensors.
Patent Literature 1 describes a touch input device which includes a touch panel which is an operation detecting sensor, and a pressure-sensitive sensor which detects a press on an operation surface. In the touch input device according to Patent Literature 1, the pressure-sensitive sensor is disposed on a surface of a lower side of the touch panel (a surface at a side opposite to the operation surface), and has the same area as that of the touch panel. Further, in the touch input device according to Patent Literature 1, a protection layer is disposed at a side of the operation surface of the touch panel.
In this case, the pressure-sensitive sensor receives a stress in response to a press on the operation surface via the protection layer and the touch sensor, and detects a pressing force corresponding to the press.
PTL 1: Japanese Patent Application Laid Open No. 5-61592